<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div class="box" id="box">元素</div>
  <ul><li>ss</li><li>22</li><li>33</li></ul>
  <script>
    var box = document.getElementById("box")
    var arrs = document.getElementsByTagName("li")
    console.log(box)
    console.log(arrs.length)
  </script>
</body>
</html>
